Method of decolorizing kaolin, clay, &amp;c.



KARL LANGENBEQK, OF WASHINGTON, DISTRICT OF COLUMBTA unrnon or nnconomzme mom, our, 860.,

' Specification of Letters Patent. Application filed September 17, 1907. Serial No. 393,417.

Pa-tented July 14, 1908.

To all whom it mag concern: Be it known that I, KARL LANGENBECK, a citizen of the United States, residing at Washington, in the District of Columbia, have invented certain new and userul'Imrovements in Methods of Decolorizing Kaoin, Clay, &c., of which the following is a specification. I

The object of this invention is to rovide a method of treating kaolin, clay, g ass-sand and like materials forthe purpose of elimi net the objectionable coloring matter or of re ucing the roportion or coloring effect of the same, w ereby the material is rendered more available for certain technical uses. a

The invention will be described 3 refer: ence to the treatment of kaolin for the purposes of preparing the same or use as a size or filling for paper or the like, for the manufacture of pottery, and for other technical pur oses: but it is to be understood that the met 0d is equallya plicable to the treatthe conversion of ferric com ounds into ferment of clays; fire-ca s, glass-sand or the like. I have foundrt at the yellowish or brownish tints of kaolin and like materials are usually associated with the presence of small proportions of iron, and are probably due to compounds in which the iron occurs in the ferric state, which compounds however cannot be effectively-or economically removed by direct treatment with dilute mineral acids. Even in cas s in which the coloring matter is relatively fugitive and is destroyed or lessened in effect by heat, I have found it to be due to iron or at least to be removed by treatment as hereinafter described, although in such cases the coloration has been commonly attributed to the presence of organic matter.

I may proceed substantially as follows: The kaolin or other material is suspended or immersed in water or in any suitable solution, and is treated therein with sulfureted hydrogen in any suitable manner, as for instance by bubblin the gas through the liquid or, sludge. The e ect of this treatment is to convert any iron compounds which may be present into ferrous sulfid, FeS. the presence of which is evidenced by a pronounced darkening or blackening of the mass, At

this stage the material consists substantially of kaolin mixed with ferrous sulfid, and it is thereafter submitted to such oxidizing con- .ditions as will convert the'ferrous sulfidinto ferrous sulfate or ferric sulfate or a mixture of these. This oxidation may be effected by the addition of small pro ortions of bleaching powder, preferably wit the usual acid addition for decomposing it by treatment with chlorin or active oxidizing agents, or even by exposure to atmospheric air. This oxidation me. in the case of certain clays containing bot iron compounds and organic coloring matter, increase the decolo'rizing effect by the destruction or transformation of the latter. The iron salt or salts produced by this treatment arefound to be readily removable by washing or leaching with water or dilute acid solutions, and the residual material is practicall white and-of hi h purity.

Instea of employing sulfureted hydro on as above described, it will be understood t at rous sulfid ma be effected the employment of suitab e metallic sulfi s.

It'will be understood that the method of treatment do :ribed above may be applied as an intermediate step in the treatment of the material for other purposes; thus the preparation of pottery bodies is accomplished y macerating or washing the clay or kaolin with water, and the elimination of the color-' g matten may be conveniently effected at this stage. 1

I claim: 7

Themethod of decolorizing kaolin, clay, or. like material containing iron, which consists in subjecting the same in presence of water to the action of a rea ent capable-of producing ferrous sulfid, an then removing the ferrous sulfid by oxidizing the same and treating the material with a suitable solvent.

n testimony whereof, I affix my signature in presence of two witnesses.

CLINTON P. 'IowNsENn, N. P. LEONARD. 

